Influence of a perpendicular magnetic field on the thermal depinning of a single Abrikosov vortex in a superconducting Josephson junction

Thermal depinning of a single vortex trapped in a superconducting Josephson junction is studied as a function of an external magnetic field perpendicular to the junction, in order to examine the conditions necessary for establishing a vortex free junction. If a thick normal metal barrier is used in a cross-strip SNIS Josephson junction, then a single vortex can be nucleated in one of the superconducting strips and systematically moved from one location to another. The location of the vortex can be determined because there is a unique connection between the location of the vortex in the junction and the Fraunhofer-like diffraction pattern of the junction. In zero applied field, it was found that the superconducting order parameter Delta/Delta0 when the vortex depins and starts to move around the film at 8.804 K is equal to 0.19. This implies that the superfluid density is 3.4%. In an applied magnetic field of 10 mG perpendicular to the junction, the vortex moves at 8.707 K where Delta/Delta 0 ~ 0.6. The shielding currents from the applied perpendicular field makes the vortex mobile at a lower temperature;The sharp steps seen previously in I0, the critical current density at zero applied field, during the nucleation process in Pb junctions, did not occur in the Nb junctions used in the present work. Once the vortex has been nucleated and begins to move, a rather a semi-continuous step-like behavior was observed both during the field cooling process and the transport current nucleation process. This was because the vortices were nucleated close to the junction\u27s edge where the there is a small spatial variation of I0. This in turn suggests a lower free energy closer to the edge of the junction due to spatial variation of the film thickness, with the films being thinner close to the edge

Magnetoelastic sensing apparatus and method for remote pressure query of an environment

A pressure sensing apparatus for operative arrangement within an environment, having: a sensor comprising a hermetically-sealed receptacle, at least one side of which has an flexible membrane to which a magnetically hard element is attached. Enclosed within the receptacle is a magnetostrictive element that vibrates in response to a time-varying magnetic field. Also included is a receiver to measure a plurality of successive values for magneto-elastic emission intensity of the sensor taken over an operating range of successive interrogation frequencies to identify a resonant frequency value for the sensor. Additional features include: (a) the magnetically hard element may be adhered to an inner or outer side of, or embedded within, the membrane; (b) the magnetostrictive element can include one or more of a variety of different pre-formed, hardened regions; (c) the magneto-elastic emission may be a primarily acoustic or electromagnetic emission; and (d) in the event the time-varying magnetic field is emitted as a single pulse or series of pulses, the receiver unit can detect a transitory time-response of the emission intensity of each pulse (detected after a threshold amplitude value for the transitory time-response is observed). A Fourier transform of the time-response can yield results in the frequency domain. Also, an associated method of sensing pressure of an environment is included that uses a sensor having a magnetostrictive element to identify a magneto-elastic resonant frequency value therefore. Using the magneto-elastic resonant frequency value identified, a value for the pressure of the environment can be identified

Magnetoelastic sensor for characterizing properties of thin-film/coatings

An apparatus for determining elasticity characteristics of a thin-film layer. The apparatus comprises a sensor element having a base magnetostrictive element at least one surface of which is at least partially coated with the thin-film layer. The thin-film layer may be of a variety of materials (having a synthetic and/or bio-component) in a state or form capable of being deposited, manually or otherwise, on the base element surface, such as by way of eye-dropper, melting, dripping, brushing, sputtering, spraying, etching, evaporation, dip-coating, laminating, etc. Among suitable thin-film layers for the sensor element of the invention are fluent bio-substances, thin-film deposits used in manufacturing processes, polymeric coatings, paint, an adhesive, and so on. A receiver, preferably remotely located, is used to measure a plurality of values for magneto-elastic emission intensity of the sensor element in either characterization: (a) the measure of the plurality of values is used to identify a magneto-elastic resonant frequency value for the sensor element; and (b) the measure of the plurality of successive values is done at a preselected magneto-elastic frequency

Magnetoelastic sensors in combination with nanometer-scale honeycombed thin film ceramic TiO2 for remote query measurement of humidity

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Ninety-Degree Chevron Osteotomy for Correction of Hallux Valgus Deformity: Clinical Data and Finite Element Analysis

Hallux valgus is a very common foot disorder, with its prevalence estimated at 33% in adult shoe-wearing populations. Conservative management is the initial treatment of choice for this condition, but surgery is sometimes needed. The 600 angle Chevron osteotomy is an accepted method for correction of mild to moderate hallux valgus in adults less than 60 years old. A modified 900 angle Chevron osteotomy has also been described; this modified technique can confer some advantages compared to the 600 angle method, and reported results are good. In the current work we present clinical data from a cohort of fifty-one female patients who had surgery for sixty-two hallux valgus deformities. In addition, in order to get a better physical insight and study the mechanical stresses along the two osteotomies, Finite Element Analysis (FEA) was also conducted. FEA indicated enhanced mechanical bonding with the modified 900 Chevron osteotomy, because the compressive stresses that keep the two bone parts together are stronger, and the shearing stresses that tend to slide the two bone parts apart are weaker, compared to the typical 600 technique. Follow-up data on our patient cohort show good or excellent long-term clinical results with the modified 900 angle technique. These results are consistent with the FEA-based hypothesis that a 900 Chevron osteotomy confers certain mechanical advantages compared to the typical 600 procedure

Influence of a perpendicular magnetic field on the thermal depinning of a single Abrikosov vortex in a superconducting Josephson junction

Thermal depinning of a single vortex trapped in a superconducting Josephson junction is studied as a function of an external magnetic field perpendicular to the junction, in order to examine the conditions necessary for establishing a vortex free junction. If a thick normal metal barrier is used in a cross-strip SNIS Josephson junction, then a single vortex can be nucleated in one of the superconducting strips and systematically moved from one location to another. The location of the vortex can be determined because there is a unique connection between the location of the vortex in the junction and the Fraunhofer-like diffraction pattern of the junction. In zero applied field, it was found that the superconducting order parameter Delta/Delta0 when the vortex depins and starts to move around the film at 8.804 K is equal to 0.19. This implies that the superfluid density is 3.4%. In an applied magnetic field of 10 mG perpendicular to the junction, the vortex moves at 8.707 K where Delta/Delta 0 ~ 0.6. The shielding currents from the applied perpendicular field makes the vortex mobile at a lower temperature;The sharp steps seen previously in I0, the critical current density at zero applied field, during the nucleation process in Pb junctions, did not occur in the Nb junctions used in the present work. Once the vortex has been nucleated and begins to move, a rather a semi-continuous step-like behavior was observed both during the field cooling process and the transport current nucleation process. This was because the vortices were nucleated close to the junction's edge where the there is a small spatial variation of I0. This in turn suggests a lower free energy closer to the edge of the junction due to spatial variation of the film thickness, with the films being thinner close to the edge.</p

The Effect of the Thermal Annealing Process to the Sensing Performance of Magnetoelastic Ribbon Materials

The magnetoelastic materials find many practical applications in everyday life like transformer cores, anti-theft tags, and sensors. The sensors should be very sensitive so as to be able to detect minute quantities of miscellaneous environmental parameters, which are very critical for sustainability such as pollution, air quality, corrosion, etc. Concerning the sensing sensitivity, the magnetoelastic material can be improved, even after its production, by either thermal annealing, as this method relaxes the internal stresses caused during manufacturing, or by applying an external DC magnetic bias field during the sensing operation. In the current work, we performed a systematic study on the optimum thermal annealing parameters of magnetoelastic materials and the Metglas alloy 2826 MB3 in particular. The study showed that a 100% signal enhancement can be achieved, without the presence of the bias field, just by annealing between 350 and 450 &deg;C for at least half an hour. A smaller signal enhancement of 15% can be achieved with a bias field but only at much lower temperatures of 450 &deg;C for a shorter time of 20 min. The magnetic hysteresis measurements show that during the annealing process, the material reorganizes itself, changing both its anisotropy energy and magnetostatic energy but in such a way such that the total material energy is approximately conserved

Magnetoelastic Ribbons as Vibration Sensors for Real-Time Health Monitoring of Rotating Metal Beams

In the current work, magnetoelastic material ribbons are used as vibration sensors to monitor, in real time and non-destructively, the mechanical health state of rotating beam blades. The magnetoelastic material has the form of a thin ribbon and is composed of Metglas alloy 2826 MB. The study was conducted in two stages. In the first stage, an experiment was performed to test the ability of the ribbon to detect and transmit the vibration behavior of four rotating blades, while the second stage was the same as the first but with minor damages introduced to the blades. As far as the first stage is concerned, the results show that the sensor can detect and transmit with great accuracy the vibratory behavior of the rotating blades, through which important information about the mechanical health state of the blade can be extracted. Specifically, the fast Fourier transform (FFT) spectrum of the recorded signal revealed five dominant peaks in the frequency range 0&ndash;3 kHz, corresponding to the first five bending modes of the blades. The identification process was accomplished using ANSYS modal analysis, and the comparison results showed deviation values of less than 1% between ANSYS and the experimental values. In the second stage, two types of damages were introduced to the rotating blades, an edge cut and a hole. The damages were scaled in number from one blade to another, with the first blade having only one side cut while the last blade had two side cuts and two holes. The results, as was expected, show a measurable shifting on the frequency values of the bending modes, thus proving the ability of the proposed magnetoelastic sensors to detect and transmit changes of the mechanical state of rotating blades in real time

Magnetoelastic Ribbons as Vibration Sensors for Real-Time Health Monitoring of Rotating Metal Beams

In the current work, magnetoelastic material ribbons are used as vibration sensors to monitor, in real time and non-destructively, the mechanical health state of rotating beam blades. The magnetoelastic material has the form of a thin ribbon and is composed of Metglas alloy 2826 MB. The study was conducted in two stages. In the first stage, an experiment was performed to test the ability of the ribbon to detect and transmit the vibration behavior of four rotating blades, while the second stage was the same as the first but with minor damages introduced to the blades. As far as the first stage is concerned, the results show that the sensor can detect and transmit with great accuracy the vibratory behavior of the rotating blades, through which important information about the mechanical health state of the blade can be extracted. Specifically, the fast Fourier transform (FFT) spectrum of the recorded signal revealed five dominant peaks in the frequency range 0–3 kHz, corresponding to the first five bending modes of the blades. The identification process was accomplished using ANSYS modal analysis, and the comparison results showed deviation values of less than 1% between ANSYS and the experimental values. In the second stage, two types of damages were introduced to the rotating blades, an edge cut and a hole. The damages were scaled in number from one blade to another, with the first blade having only one side cut while the last blade had two side cuts and two holes. The results, as was expected, show a measurable shifting on the frequency values of the bending modes, thus proving the ability of the proposed magnetoelastic sensors to detect and transmit changes of the mechanical state of rotating blades in real time

The Effect of the Thermal Annealing Process to the Sensing Performance of Magnetoelastic Ribbon Materials

The magnetoelastic materials find many practical applications in everyday life like transformer cores, anti-theft tags, and sensors. The sensors should be very sensitive so as to be able to detect minute quantities of miscellaneous environmental parameters, which are very critical for sustainability such as pollution, air quality, corrosion, etc. Concerning the sensing sensitivity, the magnetoelastic material can be improved, even after its production, by either thermal annealing, as this method relaxes the internal stresses caused during manufacturing, or by applying an external DC magnetic bias field during the sensing operation. In the current work, we performed a systematic study on the optimum thermal annealing parameters of magnetoelastic materials and the Metglas alloy 2826 MB3 in particular. The study showed that a 100% signal enhancement can be achieved, without the presence of the bias field, just by annealing between 350 and 450 °C for at least half an hour. A smaller signal enhancement of 15% can be achieved with a bias field but only at much lower temperatures of 450 °C for a shorter time of 20 min. The magnetic hysteresis measurements show that during the annealing process, the material reorganizes itself, changing both its anisotropy energy and magnetostatic energy but in such a way such that the total material energy is approximately conserved